Can you believe that the larvae in the top photo are wasps? Although they look and act a great deal like Lepidopteran caterpillars there are distinct differences if you look closely. Sawflies have more than 5 prolegs and caterpillars usually have fewer, and they lack crotchets (tiny hooks) on their prolegs and caterpillars usually have clusters of crotchets.There are many species of these wasps called sawflies, but most have certain features in common including sociality and herbivory. Some sawflies are importan pests on conifer or hardwood trees. Adult sawflies are stingless wasps. They are called sawflies because the females have a saw-like ovipositor that is used to deposit eggs in leaf tissue.

The larvae in the photo are Dusky Birch Sawflies (Croesus latitarsus). The larvae often line up along the edges of leaves and feed inward along the edges until the entire leaf is consumed. The larvae rear up when disturbed to startle predators. Some sawfly larvae also sequester defensive chemicals from the plants they feed and can spray predators if they are attacked.